Axial piston motor with bearing flushing

ABSTRACT

The invention relates to an axial piston motor constructed as a swivel-slide structure with a channel to feed cleaning fluid to the driving shaft bearings. The axial piston motor ( 1 ) comprises a swivelling cylinder drum ( 8 ) and a driving shaft ( 3 ) supported on driving shaft bearings ( 4, 5 ). The driving shaft ( 3 ) is connected to a driving shaft flange ( 6 ) to which movable pistons ( 11, 12 ) are coupled through the cylinder bores ( 9, 10 ) of the cylinder drum ( 8 ), and on which the cylinder drum ( 8 ) is supported by a central journal ( 16 ). In addition, the invention provides for a control specular element ( 18 ) with reniform control elements and a regulating device ( 26 ), by which the cylinder drum ( 8 ) together with the control specular element ( 18 ) can be swivelled. According to the improvement added by the invention, the cleaning fluid channel is taken through the setting journal ( 25 ) and control specular element ( 18 ) up to the central journal ( 16 ). The cleaning fluid channel then continues inside the central journal ( 16 ) and the driving shaft ( 3 ) and exists at the driving shaft bearings ( 4, 5 ) that require feeding.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an axial piston machine of the pivotingcarriage type of construction, with an internal bearing-flushing system.

2. Discussion of the Prior Art

The starting point of the invention is an axial piston machine, such asis known, for example, from DE 42 15 869 C1. This publishedspecification discloses an axial piston machine of the pivoting carriagetype of construction. The known axial piston machine comprises apivotable cylinder drum and a drive shaft mounted in a drive shaftbearing arrangement. The drive shaft is connected to a drive shaftflange in which pistons movable in cylinder bores in the cylinder drumare articulated and on which the cylinder drum is supported via acentral journal. There is also provided, between the cylinder drum and aclosing plate on the end face, a lens-shaped control mirror body whichhas control nodules for the cyclical connection of the cylinder bores tothe working lines. A positioning arrangement, which is not representedin detail in DE 42 15 869 C1, is provided for tilting the cylinder drum,together with the control mirror body. In order to supply the driveshaft bearing arrangement with flushing agent, a flushing duct isprovided in the central journal and in the drive shaft. The leakage oildraining out of the drive shaft bearing arrangement as a result of theflushing of the bearings is conveyed away in the direction of an openingin the housing by a vane wheel provided on the drive shaft flange.

From DE 36 38 890 C2, it is known practice to provide an axial pistonmachine of the oblique-axis type of construction having a constant,non-adjustable displacement volume, with a flushing agent duct whichextends through the central journal and the drive shaft. The flushingagent is removed, by means of a valve needle which is displaceable in apressure-dependent manner, from that control nodule of the control partwhich conducts low pressure.

However, this design solution cannot be used in axial piston machines ofthe pivoting carriage type of construction with a cylinder drum which istiltable for the purpose of varying the displacement volume, withoutproblems arising which cannot be overcome in practice. In particular, ithas turned out that malfunctions of the valve needle occur if thecontrol mirror body also impacts the stop means which determine theminimum and maximum displacement volumes in each case. The valve needlejams as a result of impact loads which arise in the process, and crackscan occur in the control mirror body In addition, the solution with anintegrated valve needle which is known from DE 36 38 890 C2 has likewiseproved unsuccessful because the bores and recesses necessary forreceiving the flushing needle lead to a weakening of the control mirrorbody and the feeding pressure protection for the flushing agent is notconstant because of the rotation and the pivoting movement of thecylinder drum and of the control mirror body. A further disadvantage isthat the feeding pressure setting for the flushing agent cannot be setfrom outside, since the feeding pressure valve is not accessible fromoutside and the flushing valve integrated into the control mirror bodydepends upon the nominal size, since the distance between the controlnodules is different for each nominal size of the axial piston machines.It has also turned out that the quantity of flushing agent introducedinto the flushing duct by the flushing valve integrated into the controlmirror body is inadequate for some applications.

For the reasons mentioned above, the solution known from DE 36 38 890 C2for axial piston machines with a constant displacement volume has notproved successful in practice in the case of axial piston machines ofthe pivoting carriage type of construction with variable displacementvolume.

SUMMARY OF THE INVENTION

The underlying object of the invention, therefore, is to make availablea suitable flushing agent supply system for an axial piston machine ofthe pivoting carriage type of construction.

Underlying the invention is the knowledge that the flushing agent ductfor supplying the drive shaft bearing arrangement with flushing agentand, optionally, for additionally flushing the housing, can be routed,in a simple manner, through the positioning journal and the controlmirror body as far as the central journal. The flushing and feedingpressure valve can then be disposed out side the control mirror body, afact which substantially simplifies the design of the latter, so thatthe mechanical strength of the said control mirror body is not weakenedby the measures necessary for constructing the flushing duct. Inaddition, the advantage arises that a flushing and feeding pressurevalve which can be provided externally can be set from the outside andthe quantity of flushing agent introduced into the flushing agent ductcan be adapted to the actual demand in a simple manner.

According to the invention, the central bore in the control mirror bodyfor receiving the positioning journal may, at the same time, be part ofthe flushing agent duct, so that no design changes are necessary at thecontrol mirror body for constructing the flushing agent duct. Accordingto another aspect, there may be constructed in the positioning journal abore which forms the flushing agent duct in this region and opens intothe central bore in the control mirror body. Under these circumstances,the only modification to the positioning journal which is necessary forthe flushing agent duct is the construction of the said bore. The boremay be constructed with a diameter which is so small that the mechanicalstrength of the positioning journal is insignificantly weakened by thismeasure, in particular by less than 1%.

According to a further aspect, the positioning arrangement may have ahydraulically actuatable positioning piston in which a transverse boreis constructed in order to receive the positioning journal. According toa still further aspect, the positioning piston may be guided in alongitudinal bore which is constructed in a closing plate and isprovided with a longitudinal groove into which the bore in thepositioning journal opens, either directly or else indirectly via thetransverse bore in the positioning piston. Under these circumstances,the longitudinal groove guarantees a supply of flushing agent in anyposition of the positioning piston and of the positioning journalinserted in the latter. Under these circumstances, connection of thebore in the positioning journal to the longitudinal groove provided inthe closing plate is ensured, irrespective of the pivoting position ofthe cylinder drum, of the control mirror body and of the positioningjournal inserted in the positioning piston. According to a specificfeature, the longitudinal groove may be connected to an in-feed line forthe flushing agent. The flushing and feeding pressure valve forintroducing the flushing agent into the flushing agent duct may bemounted externally on the closing plate at the orifice of the in-feedline. Under these circumstances, the flushing and feeding pressure valveis particularly easily settable and accessible from outside.

According to another feature, the flushing agent duct according to theinvention may, as well as serving to supply the drive shaft bearingarrangement with flushing agent, at the same time also serve to flushthe housing. This results in a particularly favourable heat balance forthe axial piston machine, since the heat due to energy losses from theaxial piston machine is conducted away, together with the flushingagent, by the agent itself.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplified embodiment of the invention will be described in greaterdetail below with reference to the drawings, in which:

FIG. 1 shows a longitudinal section through an exemplified embodiment ofthe axial piston machine according to the invention; and

FIG. 2 shows a section along the line A—A in FIG. 1.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows, in an axial longitudinal section, an exemplifiedembodiment of an axial piston machine according to the invention of thepivoting carriage type of construction.

A drive shaft 3 is rotatably mounted in a housing 2 of the axial pistonmachine 1 via two rolling bearings 4 and 5. In the exemplifiedembodiment, a drive shaft flange 6 is formed onto the drive shaft 3 inone piece. A cylinder drum 8 is disposed in the interior 7 of thehousing so as to be pivotable about a pivoting axis perpendicular to theplane of the drawing. A number of cylinder bores 9, 10 disposed over apartial circle at equal intervals are provided in the cylinder drum 8.Displaceably guided in the cylinder bores 9, 10 are pistons 11, 12 whichare shaped-out to form spherical heads 13, 14 outside the cylinder drum8. The spherical heads 13, 14 of the pistons 11, 12 are articulated inspherical bearings 15 in the drive shaft flange 6.

The cylinder drum 8 is rotatably and tiltably mounted on the drive shaftflange 6 via a central journal 16. Disposed between a closing plate 17and the cylinder drum 8, on that side of the said cylinder drum 8 whichfaces away from the drive shaft flange 6, is a control mirror body 18which, in the exemplified embodiment, is of lens-shaped construction.The cylinder drum 8 is pre-tensioned against the control mirror body 18,or rather the closing plate 17, via a spring 19 provided in the centraljournal 16. The central journal 16 likewise has a spherical head 20which is rotatably and pivotably mounted in another spherical bearing 21in the drive shaft flange 6.

When the cylinder drum 8, which is represented in FIG. 1 in the positionin which it is pivoted out to the maximum extent, is tilted, the controlmirror body 18 serves as a pivoting carriage. When the cylinder drum 8is shifted, a partially cylindrical or spherical boundary face 22 on thecontrol mirror body 18, which boundary face is located opposite the saidcylinder drum 8, slides along on a correspondingly shaped-out slidingface 23 on the closing plate 17. Under these circumstances, theset-screw 24 a serves to set the minimum displacement volume of theaxial piston machine 1.

The control mirror body 18 has a central bore 24 in which a positioningjournal 25 is inserted in such a way that the said positioning journal25 is pivotable and axially displaceable in the central bore 24 of thecontrol mirror body 18 in order to balance out the pivoting movement ofthe latter.

For the purpose of hydraulically adjusting the pivoting angle of thecylinder drum 8, there is provided a positioning arrangement which isprovided, in a general manner, with the reference symbol 26 and whichcomprises a positioning piston 28 which is displaceable in alongitudinal bore 27 in the closing plate 17. The positioning journal 25is inserted in a transverse bore 29 in the positioning piston 28. Thepositioning piston 28 can be acted upon, via a positioning pressure linewhich can be connected to a connection 30, by a positioning pressure insuch a way that the positioning piston 28 is displaceable against arestoring spring 31. Under these circumstances, the axial piston machine1 is pivoted back towards smaller displacement volume.

According to the invention, the axial piston machine 1 is provided witha flushing agent duct for supplying flushing agent to the drive shaftbearing arrangement 4, 5. The flushing agent duct comprises an in-feedline 40 which is provided in the closing plate 17 and to which aflushing and feeding pressure valve 41 is connected. The flushing andfeeding pressure valve 41 is disposed externally on the closing plate 17and is therefore easily accessible from outside for the purpose ofsetting the pressure and quantity of the flushing agent. The in-feedline 40 opens into a longitudinal groove 42 which is providedperipherally on the longitudinal bore 27. In the positioning journal 25,there is also provided a bore 43 which, on the side remote from thecontrol mirror body 18, either opens directly into the longitudinalgroove 42 or else, as in the case of the exemplified embodimentrepresented in FIG. 1, opens indirectly into the said longitudinalgroove 42 via the transverse bore 29. The length of the longitudinalgroove 42 is so dimensioned that a connection between the bore 43 in thepositioning journal and the said longitudinal groove 42 is ensured inany pivoting position of the cylinder drum 8.

In order to better elucidate the way in which the flushing agent duct isrouted in this region, a section along the line A—A is represented inFIG. 2. What is shown is a cross-section through the closing plate 17and through the longitudinal bore 27 provided in the said closing plate17 for guiding the positioning piston 28. Also visible is thepositioning journal 25 which is inserted in the transverse bore 29 inthe positioning piston 28 and which is represented only in the form of adetail. As already described, the positioning journal 25 has an axialbore 43 which is part of the flushing agent duct according to theinvention. As can likewise be perceived from FIG. 2, the in-feed line 40is connected to the longitudinal groove 42 provided peripherally on thelongitudinal bore 27. The bore 43 in the positioning journal 25 opensindirectly into the longitudinal groove 42 via the transverse bore 29 inthe positioning piston 28, which transverse bore is not filled up by thepositioning journal 25 in the region 44. However, it is also possiblefor the bore 43 in the positioning journal 25 to open directly into thelongitudinal groove 42, if the said positioning journal 25 completelyfills up the transverse bore 29.

The mechanical strength of the positioning journal 25 is impaired onlyinsignificantly by the bore 43 provided in the said journal. Thediameter of the bore 43 can be of such small dimensions that the resultis a reduction in mechanical strength of less than 1%. Nor is themechanical strength of the control mirror body 18 affected by themeasures according to the invention, since the solution according to theinvention does not necessitate any design change in the control mirrorbody 18.

As can be perceived from FIG. 1, the flushing agent duct extends onwardsthrough the central bore 24 in the control mirror body 18. In thisconnection, it should be emphasised that the central bore 24 in thecontrol mirror body 18, which central bore is present in any case, alsotakes on the function of conducting-in the flushing agent without anyfurther modification. The flushing agent duct extends onwards through anaxial bore 44 in the cylinder drum 8 and a bore 45 in the spring plate46, only to open into the spring compartment 47 of the central journal16. After this, a central bore 48 extends, in the central journal 16,from the spring compartment 47 as far as the spherical bearing 21.Provided in the drive shaft 3 are further connecting ducts 49, 50 and 51which emerge directly in the region of the rolling bearings 4, 5. At thespherical bearing 21, both the central bore 48 in the central journal 16and also the mouth of the connecting duct 49 are provided withtrumpet-shaped widened portions in order to ensure that a flux offlushing agent is made possible in any tilting position of the cylinderdrum 8.

After flowing through the drive shaft bearing arrangement 4, 5, theflushing agent flows into the interior 7 of the housing, only to leavethe latter as leakage fluid via the opening 52 in the housing. Thissimultaneously guarantees flushing of the housing which serves, interalia, to conduct away the heat due to energy losses. In this way, theheat balance of the axial piston machine 1 is improved.

In order to better elucidate the invention, the flux of flushing agentis represented by the arrows drawn in in FIG. 1.

The invention is not limited to the exemplified embodiment represented.In particular, the influx of flushing agent to the positioning journal25 could also take place in some other way, for example via thepositioning piston 28.

What is claimed is:
 1. An axial piston machine (1) of the pivotingcarriage type of construction, comprising a pivotable cylinder drum (8),a drive shaft (3), a drive shaft bearing arrangement (4,5) having saiddrive shaft mounted therein for connection to a drive shaft flange (6),pistons (11, 12) articulated on said flange (6) being moveable incylinder bores (9, 10) in the cylinder drum (8), a central journal (16)supporting said cylinder drum (8) on said flange (6), a flushing agentduct (45, 47 to 51) for supplying the drive shaft bearing arrangement(4, 5) with flushing agent being arranged in the central journal (16)and in the drive shaft (3), a control mirror body (18) having controlnodules in order to connect the cylinder bores (9, 10) cyclically to ahigh-pressure line and a low-pressure line, a positioning arrangement(26) for tilting the cylinder drum (8) in conjunction with the controlmirror body (18), a positioning journal (25) for connecting thepositioning arrangement (26) to the control mirror body (18), saidpositioning arrangement (26) comprising a hydraulically actuatablepositioning piston (28) which has a transverse bore (29) having thepositioning journal (25) inserted therein, said flushing agent duct (43,24) being conducted through the positioning journal (25) and the controlmirror body (18) up to the central journal (16), said machine (1 havinga housing (52) flushed with flushing agent through the flushing agentduct (40-43, 24, 44, 45, 47-51), an opening in said housing (52)for thesimultaneous egress of the flushing agent from the housing (2) of theaxial piston machine (1), a closing plate (17) includes a longitudinalbore (27), the positioning piston (28) being guided in said longitudinalbore, said closing plate (17) including at least one longitudinal groove(42) into which opens the bore (43) in the positioning journal (25)either directly or indirectly via the transverse-bore (29) in thepositioning piston (28), an in-feed line (40) is arranged in the closingplate (17) for feeding the flushing agent into the longitudinal groove(42), wherein the in-feed line (40) is connected to a flushing andfeeding pressure valve (41).
 2. An axial piston machine according toclaim 1, wherein the control mirror body (18) has a central bore (24) inwhich the positioning journal (25) is guided, and which central bore isa part of the flushing agent duct.
 3. An axial piston machine accordingto claim 1, wherein a bore (43) which is part of the flushing agent ductopens into the central bore (24) in the control mirror body (18), saidbore (43) being formed in the positioning journal (25).